The present invention relates to a centralized lubrication system for feeding lubricant in predetermined quantities to a plurality of points of use such as bearings in vehicles and machinery.
Various centralized lubrication systems have heretofore been proposed for distributing and injecting lubricant to a plurality of bearings or the like. Some centralized lubrication systems such as disclosed in U.S. Pat. Nos. 3,995,717 and 4,520,902, utilize a single positive displacement lubricant pressure pump, and a plurality of distributing valves that are connected to the pressure pump and arranged to distribute the pressurized lubricant to a plurality of points of use. However, problems are encountered in using a lubricant pump for pumping viscous lubricants or greases. Some other central lubrication systems such as disclosed in U.S. Pat. No. 3,724,600 pressurize the grease in supply tanks and feed the pressurized grease through distribution and metering valves to the various points of use under the pressure of the grease from the supply tanks. This not only requires grease supply tanks capable of withstanding relatively high pressures, but also limits the pressure at which the grease is fed to the points of use. U.S. Pat. No. 2,719,603 discloses a lubricant dispensing system wherein grease is fed to a distributing valve and a pneumatically actuated injector and in which the injector actuating piston has an area that is large as compared to the area of the injector piston, to increase the pressure on the grease supplied to the points of use. However, this arrangement requires a relatively complex injector and valving arrangement and seals which are capable of preventing leakage of air into the grease.